REVIEW:
LG Flatron M2794D
Part 7

Brightness distribution

The measured brightness deviation at the upper edge of the screen is a maximum of 11 percent, whilst the equivalent deviation at the lower edge of the screen is 27 percent. The average deviation is 8 percent.

The brightness values (left picture) and the colour temperature (right picture) were measured at 15 points.

This is no longer satisfactory in view of the high deviation in the lower left corner, but the deviations in the centre of the screen are considerably lower. The average deviation drops to around 6 percent here. After calibration with a target gamma of 2,2, this value is retained in the middle area of the panel. At the top edge, the gamma increases to 2,3, whilst it drops to 2,1 at the bottom.

According to LG, the contrast ratio for the M2794D is 1.000:1 and should increase to 20.000:1 when dynamic contrast regulation is used. As with implementations from other manufacturers, we were unable to verify this value in the course of the test. In the factory settings, the LG M2794D almost exactly meets the manufacturer’s value at 985:1. After successful calibration to a brightness of 140 cd/m², the contrast drops just slightly to a still good value of 868:1.

In the standard settings, the contrast is 100 percent and the brightness 50 percent. In this setting, hues are visible from the fourth level. At the other end of the spectrum, the monitor resolves up to level 250. At this point, the brightness and contrast regulation come into play. Since the brightness regulator on the LG M2794D only influences the black level, we hoped for additional, darker hues after increasing the values. Reducing the contrast slightly reduces the white level and should make brighter hues visible in this case. With a brightness of 53 percent and a contrast of 95 percent, all dark hues are visible. Bright hues are still resolved up to the third last level. A brightness of 54 percent gives rise to strong flickering for a dark screen because the maximum black is only dark grey and the FRC implementation unfortunately steps in.

The dynamic contrast regulation hides behind the "Extended contrast" setting and can only be used via the video inputs. Unfortunately, the implementation here is very aggressive. Visible pumping of the brightness already reduces usefulness in the low setting. In addition, the constant pushing out of the black and white levels is irritating. Therefore, you should avoid using this function, since the contrast ratio is already high enough without dynamic interference from the monitor’s electronics.

We tested the differentiation of bright and dark grey gradients using suitable test images.

At 100 percent backlight brightness, we measured a light density of 443 cd/m². This even exceeds the manufacturer’s figure of 400 cd/m². However, such high values are not necessary in normal working environments. In this setting, the black point is 0.49 cd/m².

The maximum brightness allows us to fear that the more important minimum brightness will be comparatively high. In fact, we achieved a value of exactly 140 cd/m² using on-board means. This is generally sufficient but is still too high for use in dark environments.

The brightness can be reduced somewhat through reducing the white level in reducing the contrast value, but this then gives rise to a "dirty" white.

The brightness regulator also affects the white level under 50 percent. At a brightness of 0 percent (backlight brightness also at 0 percent), the maximum brightness is 77 cd/m². However, the black and white levels are then completely skewed and it is no longer possible to make sensible use of the screen.

Viewing angle

The maximum viewing angle of the LG M2794D is 170 degrees horizontal and 160 degrees vertical according to the manufacturer. These details are based on a resting contrast of 10:1. Unfortunately, these values for TN panels generally prove to be completely exaggerated in reality and are therefore only significant to a limited extent.

The actual subjective viewing angle stability without visible colour flaws, negative effects or visible reductions in brightness is more important than the viewing angles with regard to the resting contrast. What use is a 170 degree viewing angle at a resting contrast of 10:1 if the image demonstrates a clear brownish staining when viewed from the side?

Viewing angles on the LG M2794D.

The TN panel on the LG M2794D cannot reinvent the wheel, but delivers exactly the expected results. In the horizontal, the viewing angle stability is large enough to present an image with only minimal colour errors at a suitable distance, even to several viewers.

In the vertical, the limitations are considerably larger, especially with regard to deviations at the lower end. At some point, the colours here merge into the negative. Even before this, visible losses of saturation and contrast arise.

With a size of 27 inches, you are already crossing a critical limit at the usual working distance (40 to 60 cm), at least when we consider the current development stage of this panel technology. Thus, colour errors cannot be avoided completely despite optimal viewing angles. The LG M2794D can still achieve a satisfactory rating in terms of viewing angle.